1. Field of the Invention
The present invention relates generally to a process and apparatus for making use of atmospheric plasma reactions and, more specifically, to a process and apparatus for making use of atmospheric-pressure plasma reactions capable of modifying the surface of powder through use of a very stable discharge plasma, at atmospheric pressure, with high efficiency.
2. Statement of the Prior Art
As generally well-known in the art, plasma is a gas in which there are positive ions and free negative electrons and therefore is electrically neutral, and that plasma differs from a neutral gas in properties. Such a plasma may be artificially obtained by gas discharge.
Incidentally, it is well-known that plasma may be applied to forming films, making use of low-pressure glow discharge plasma, or to surface modification or denaturation, and so are widely used in various industrial fields. One typical surface treatment using a low-pressure glow discharge plasma is a so-called organic plasma technique, in which thin-film making and surface modification or denaturation are achieved by making use of an organic compound gas plasma. In addition, it has been proposed to make use of plasma in a vacuum vessel to produce diamond powders or ultrafine powders or to achieve surface modification or denaturation.
Problems with such conventional surface treatments using low-pressure glow discharge plasma, however, include the requirement for low-pressure vacuum equipment and like other installation due to reactions taking place at as low as 10.sub.-5 to 10.sup.- Torr, as well as the large amount of time and high production costs required due to discontinuous (batch) treatments.
Problems associated with the surface treatment of powders, etc. include complicated equipment, much treating time, and troublesome processing steps requiring the need for waste water disposal, because the surfaces of pigments are wet-treated with resins, acids, alkalis, and solution aerosols containing surface active agents, etc.
In view of the problems mentioned above, it is therefore an object of this invention to provide a process and apparatus for making use of atmospheric-pressure plasma reactions which are of so increased reactivity at atmospheric pressure that the surfaces of large amounts of powders can be treated inexpensively in a gas phase, making use of a reaction gas plasma of great stability.